The osteogenic capability of any biomaterial is governed by a number of critical surface properties such as surface energy, surface potential, and topography. Prior work suggested that the Si-Y-O-N phase(s) present in the form of a thin (<150 nm), interrupted film at the surface of an annealed silicon nitride bioceramic may be responsible for an observed upregulation of osteoblastic activity due to passive surface properties and dissolution of chemical species. In this study high- resolution analytical electron microscopy was utilized to identify the Si-Y-O-N phase present on the annealed silicon nitride surface, and dissolution studies were employed to elucidate mechanisms of the material's favorable cell interactions. Si3N4 discs (12.7 mm diameter × 1 mm thick) containing Y2O3 and Al2O3 sintering aids were processed using conventional techniques and subsequently subjected to annealing in a nitrogen atmosphere. Pre-cultured SaOS-2 osteosarcoma cells at a concentration of 5 × 105 cells/ml were seeded onto sterile polished nitrogen-annealed Si3N4 discs in an osteogenic medium consisting of DMEM supplemented with about 50 µg/mL ascorbic acid, 10 mM β-glycerol phosphate, 100 mM hydrocortisone, and 10% fetal bovine calf serum. The samples were incubated for up to 7 days at 37°C with two medium replenishments. Transmission electron microscopy (TEM) images were acquired from focused ion beam (FIB)-prepared samples using a Hitachi HF-3300 TEM (300 kV). Scanning transmission electron microscopy (STEM) images were recorded using a Nion UltraSTEM 100 (60 kV). STEM high-angle annular dark-field (HAADF) imaging and energy dispersive X-ray spectroscopy (EDS) analyses were performed on a JEOL JEM2200FS (200 kV) equipped with a third-order CEOS aberration corrector and a Bruker XFlash silicon drift detector.Introduction
Materials and Methods
The purpose of this study was to examine five-year outcomes of patients previously enrolled in a non-operative rotator cuff study. Patients with chronic, full-thickness rotator cuff tears (demonstrated on imaging) who were referred to one of two senior shoulder surgeons were enrolled in the study between October 2008 and September 2010. Patients participated in a comprehensive non-operative, home-based treatment program. After three months patients were defined as “successful” or “failed”. “Successful” patients were essentially asymptomatic and did not require surgery. “Failed” patients were symptomatic and consented to surgical repair. All patients were followed up at one year, two years, and five-plus years. Original results of our study showed that 75% of patients were treated successfully with non-operative treatment, while 25% went on to surgery. These numbers were maintained at two-year follow-up (previously reported) and five-year follow-up. At five+ years, 88 patients were contacted for follow-up. Fifty-eight (66%) responded. The non-operative success group had a mean RC-QOL score of 80 (SD 18) at previously reported two-year follow-up. At five-year follow-up this score did not decrease (RCQOL = 82 (SD 16)). Furthermore, between two and five years, only two patients who had previously been defined as “successful” became more symptomatic and underwent surgical rotator cuff repair. From the original cohort of patients, those who failed non-operative treatment and underwent surgical repair had a mean RC-QOL score of 89 (SD 12) at five-year follow-up. The operative and non-operative groups at five-year follow-up were not significantly different (p = 0.07). Non-operative treatment is an effective and lasting option for many patients with a chronic, full-thickness rotator cuff tear. While some may argue that non-operative treatment delays inevitable surgical fixation, our study shows that patients can do extremely well over time.
